The present invention relates to the concentration of mineral ores by froth flotation and more particularly to the concentration of a sulfide ore by froth flotation.
It is common practice in froth flotation to utilize chemical reagents in order to enhance concentration of a desired fraction of an ore subjected to the process. For example, a chemical collector which is selectively adsorbed on the surface of the particles to be collected or a frothing agent or frother for enhancing the froth texture are but two of the various types of chemical reagents which generally are used in froth flotation for beneficiation of ores. For example, sulfide ores have been beneficiated traditionally by employment of a double flotation process with multiple re-cleaning stages. The sulfide ore first is comminuted and classified to the optimum particle size for admission to the first stage of the flotation process. In the first flotation stage (so-called rougher or bulk float), the sulfide mineral values are separated from various silica and silicate gangue materials by utilization of a frother and a xanthate salt or other thiol collector. The resulting sulfide mineral concentrate, typically a mixture of various sulfide minerals, may be ground further to a fine particle size and subjected to a second stage (cleaner or differential flotation) wherein the various mineral sulfides are again floated for selective recovery of one valuable sulfide mineral from other sulfide minerals contained in the admixture thereof, or to upgrade the quality of the concentrate to obtain a desired grade product. For example, molybdenum sulfide and copper sulfide collected in the rougher float can be separated from each other, e.g., by depressing the copper sulfide values utilizing reagents such as sodium hydrogen sulfide, Nokes reagent, and the like, followed by flotation of the molybdenum values. The float accomplishes differential separation typically by pH adjustment of the pulp and/or addition of specific depressants, activators, modifiers, or like conventional techniques.
Relative to the rougher float, xanthate or other thiol collectors can be rather selective in separating sulfide values from oxide impurities, especially in the presence of a frothing agent such as methyl isobutyl carbinol (MIBC) or pine oil. Molybdenum sulfide ore, however, generally does not require such a thiol-containing collector; however, non-polar hydrocarbon oils typically are used as collectors. A variety of conditioning and modifying reagents, though, have been proposed in the sulfide flotation field.